Ensuring quality interaction between a patient and their respiratory treatment apparatus can be significant. For example, some respiratory treatment apparatus provide a higher pressure during inspiration than during expiration. In such a case, the apparatus may attempt to synchronize the generated change in pressure with the patient's respiration cycle.
For example, in the case of a pressure treatment apparatus for treatment of sleep disordered breathing (e.g., a bi-level positive airway pressure apparatus), the controller may be configured to generate a lower pressure during expiration for patient comfort. Such expiratory pressure relief is described in U.S. Pat. No. 7,128,069, the entire disclosure of which is incorporated herein by reference.
In the case of a ventilator, synchronization between a patient and the apparatus can be critical to minimize the work of breathing of the patient. Increased work of breathing caused by patient-ventilator asynchrony is associated with negative patient outcomes and has been shown to be highly prevalent; studies have shown up to 47% of ventilator delivered breaths may be asynchronous.
In some devices, detecting inspiratory flow with a flow sensor or a decrease in pressure with a pressure sensor may serve as tests for triggering the delivery of inspiratory pressure. The detection of a cessation of patient inspiration, such as by detecting a peak flow or a portion thereof, may then serve as test for cycling to an expiratory pressure level. Additionally, the running of a backup timer may serve as a basis for triggering an apparatus to deliver inspiratory pressure.
It may be desirable to develop further methods and devices for automating synchronization that may improve respiratory treatment apparatus.